The invention relates to a vehicle with a bumper which is attached to the vehicle transverse to the longitudinal direction of the vehicle via at least one deformation element. The deformation element exhibits two first side walls that are spaced apart, and are jointed together via two second side walls that are spaced apart. The first and second side walls feature first and second grooves that run transverse to the longitudinal direction of the vehicle and are arranged in pairs opposite each other, each in a common plane.
A variety of means for attaching a bumper to a vehicle are known. In order to increase the energy absorbing capacity of the bumper in an accident, it is also known to attach the bumper to the longitudinal beams of the vehicle via deformation elements.
In a known deformation element of the kind mentioned above, two essentially U-shaped parts made of steel sheet are fitted together to make a closed cross-section such that the flanges of the U-shaped parts overlap in pairs, and are joined together by resistance welding at these overlapping regions. Grooves are provided on all four side walls over the whole breadth of the side walls, whereby the first and second grooves lie in the first and second side walls, all in the same plane.
The above mentioned deformation elements according to the state of the art do not exhibit excellent capacity for absorbing energy on collision with the bumper. A further disadvantage of the above mentioned known deformation element is the accumulation of material in the middle of the two side walls, which on collision results in pronounced asymmetric deformation of the deformation elements bending away from the general longitudinal direction of the vehicle.
The object of the present invention is to develop further a deformation element of the kind mentioned above, in such a way that the capacity to absorb the energy of deformation developed on collision with the bumper is greater than with comparable deformation elements. In addition, the deformation element should be simple and cost favorable to produce.
That objective is achieved by way of the invention in that the first grooves extend over the whole breadth of the first side walls, and the second grooves extend over only a middle part of the second side walls, leaving a free region at both edges, whereby the first grooves are arranged in pairs in first planes and the second grooves are arranged in pairs in second planes situated between two subsequent first planes.
The arrangement according to the invention of the grooves in the side walls leads to an increase in the capacity to absorb energy of deformation developed on collision with the bumper. As a result of the second grooves in the second side walls arranged between first grooves in the planes of the first side wailsxe2x80x94which in contrast to the first grooves do not extend over the whole breadth of the side wallsxe2x80x94deformation initiated by the first grooves is limited by preventing inward directed folding, and further absorption of energy takes place but not until a second step by further deformation up to the next plane with further first grooves. The deformation behaviour of the deformation element according to the invention is improved further in thatxe2x80x94in contrast to the state of the art deformation element mentioned at the startxe2x80x94the accumulation of material does not lie in the middle of the side wall areas but in the peripheral areas of the box-like deformation element.
The first and/or the second side walls are preferably inclined in pairs running together in the longitudinal direction of the vehicle. The result of this is that, on towing the vehicle in curvesxe2x80x94when the direction of pulling is different from the longitudinal axis of the vehiclexe2x80x94the force being transferred from the longitudinal beam to the towing bracket runs through one of the two first side walls. On the other hand the transfer of force in a collision, preceded by a braking action in which the bumper is lowered, takes place via one of the second side walls.
Usefully, the second side walls are joined together at the end facing the bumper via a strut running transverse to the longitudinal direction of the vehicle. This results in a single middle part which as a whole is simpler to manufacture.
The strut preferably exhibits an opening and a tube-shaped part which on the one hand penetrates the opening and is attached to an insert that rests against the inside of the second side walls and strut and is fixed to the second side walls and/or strut, and on the other hand features an inner thread for releasably screwing in a towing hook.
At their ends remote from the bumper, the first and/or the second side walls are preferably bent outwards in the form of a flange to form an integral attachment plate, while forming an edge.
Reinforcing grooves may run transverse to the edges formed by bending. These prevent possible deformation of the deformation element in the region of the flange.
Usefully, bent connecting strips on the second side walls lie against and are joined to the inside of the first side walls.
At the end facing the bumper, the first side walls are usefully shaped to form an attachment means for the purpose of attaching the bumper.
Under collision conditions, in order to prevent the deformation element from deforming first in the region of the connection to the longitudinal beam of the vehicle, and instead as close as possible to the bumper mounting, at least one pair of the first grooves situated in the region of the first side walls remote from the bumper can be pressed flat at the edges.
The bumper is preferably a section made of an aluminium alloy, the deformation element is usefully made of steel sheet.